Correct --persistent_worker arg constraint check

Correct --persistent_worker arg constraint check

Previously the args were normalized to change an arg with `=` into
separate args. That normalization was removed in
https://github.com/dart-lang/sdk/commit/e321439470ec016e9532afe57b7f2891c0282d83

This fixes an issue with using the analyzer in worker mode on the
current SDK.

- Allow the case where there are 3 args and one of them starts with
  --dart-sdk rather than require it to be the entire string
- Split into two bools with more descriptive names and refactor from an
  if/else chain into a composed condition

R=jakemac@google.com

Committed: https://github.com/dart-lang/sdk/commit/56ad714d6b179839f1ced976bd5d5500f814a482

[Nate Bosch, 2017-03-08 00:31:52]

nbosch@google.com changed reviewers:
+ danrubel@google.com, jakemac@google.com

[jakemac, 2017-03-08 15:24:08]

lgtm

[Nate Bosch, 2017-03-08 20:10:30]

Description was changed from

==========
Correct --persistent_worker arg constraint check

Previously the args were normalized to change an arg with `=` into
separate args. That normalization was removed in
https://github.com/dart-lang/sdk/commit/e321439470ec016e9532afe57b7f2891c0282d83

This fixes an issue with using the analyzer in worker mode on the
current SDK.

- Allow the case where there are 3 args and one of them starts with
  --dart-sdk rather than require it to be the entire string
- Split into two bools with more descriptive names and refactor from an
  if/else chain into a composed condition
==========

to

==========
Correct --persistent_worker arg constraint check

Previously the args were normalized to change an arg with `=` into
separate args. That normalization was removed in
https://github.com/dart-lang/sdk/commit/e321439470ec016e9532afe57b7f2891c0282d83

This fixes an issue with using the analyzer in worker mode on the
current SDK.

- Allow the case where there are 3 args and one of them starts with
  --dart-sdk rather than require it to be the entire string
- Split into two bools with more descriptive names and refactor from an
  if/else chain into a composed condition

R=jakemac@google.com

Committed:
https://github.com/dart-lang/sdk/commit/56ad714d6b179839f1ced976bd5d5500f814a482
==========

[Nate Bosch, 2017-03-08 20:10:31]

Committed patchset #1 (id:1) manually as
56ad714d6b179839f1ced976bd5d5500f814a482 (presubmit successful).